The present invention relates to a composite apparatus which includes in combination a secondary ion mass spectrometry instrument (hereinafter referred to as SIMS instrument) using an ion beam and a scanning electron microscope (hereinafter referred to as SEM) using an electron beam, and more particularly to a composite apparatus with SIMS instrument and SEM provided with a liquid metal ion source which effects a local analysis of a submicron region as well as a high-resolution observation of the same location as the region to be analyzed and an SEM which effects a high-resolution observation of the same location as the region to be analyzed.
In an SIMS instrument, an ion beam emitted from an ion source is used as a primary beam with which a specimen is irradiated. In an SEM, on the other hand, an electron beam is used as a primary beam.
An ion source for the conventional SIMS instrument which is widely used a duo-plasmatron type ion source using a plasma or a surface ionization type ion source using a surface ionizing mechanism. However, such an ion source is not suitable for local analysis of a submicron region (in the order of several-thousands angtroms) since the source has a relatively large diameter on the order of 0.2 to 1 mm .phi..
In recent years, a liquid metal ion source has been developed and put into practical use as an ion source which has a high brightness and a minute point source (having a spot diameter not greater than several-hundreds angstroms). In the liquid metal ion source, a metal in a melted state is supplied to the tip (or pointed end) of a needle-like chip having a diameter on the order of microns and a strong electric field is applied to the tip of the needle-like chip to form a sharp cone of melted metal, thereby causing ion emission based on a field emission mechanism.
However, an apparatus having plural kinds of ion sources and which is capable of properly selecting any one of those ion sources through a simple operation such as a change-over operation has not bee known. On the other hand, a composite electron beam apparatus having an SIMS instrument using an ion source and an SEM using an electron beam has been disclosed by, for example, JP-A-59-68159. The ion source used in the SIMS instrument of the disclosed composite electron beam apparatus is a duo-plasmatron type ion source or a surface ionization type ion source. There has not been an SIMS instrument which has a liquid metal ion source in addition to the duo-plasmatron type ion source or the surface ionization type ion source.
As mentioned above, there have been neither an SIMS instrument which has a liquid metal ion source and an ion source other than the liquid metal ion source nor a composite apparatus with SIMS instrument and SEM which has a liquid metal ion source and an electron beam source. Therefore, the following problems exist.
(1) In the case where it is desired to make a local analysis of a submicron region which cannot be analyzed by a duo-plasmastron type ion source or a surface ionization type ion source, the ion source must be exchanged for a liquid metal ion source, thereby requiring a long time for the ion source exchange, exhaustion, beam axis adjustment, etc.
(2) In the case where it is desired to conduct a local analysis using an ion source and a high-resolution observation of the same location as a region to be analyzed, two apparatuses or an SEM and an SIMS instrument must be used, thereby requiring a long time for specimen exchange, exhaustion, beam axis adjustment, etc.
(3) In general, an SIMS instrument having as an ion source a duo-plasmatron type ion source or a surface ionization type ion source is provided with a primary ion separating device for eliminating impurity ion beams or neutral particle beams included in the desired ion beam. Therefore, even if one tries to merely install a liquid metal ion source into the conventional composite ion beam apparatus having the duo-plasmatron type ion source or the surface ionization type ion source, an ion beam emitted from the liquid metal ion source will be affected by a deflection magnetic field originating from a mass separation magnetic field in the primary ion separating device so that a deflection aberration is increased and hence the astigmatism of the ion beam will become large, thereby making a local analysis of a submicron region which is characteristic of the liquid metal ion source impossible.
(4) In the case where a local analysis of a submicron region is to be made by use of a liquid metal ion source, it is necessary to change ion seeds such as Ga.sup.+, Li.sup.+ and Au.sup.+ in order to enhance the detection sensitivity in accordance with the electronegativity of an element to be measured. In the conventional SIMS instrument, liquid metal ion sources for various ion seeds must be exchanged on each occasion, thereby requiring a long time for ion source exchange, exhaustion, beam axis adjustment, etc.